1. Field of the Invention
The present invention relates to a disinfection method for a dialysis machine.
2. Description of the Related Art
The principal functions of a dialysis machine are preparing a dialysis liquid, supplying dialysis liquid to a dialyser, and removing the used liquid (mixture of dialysis liquid charged with the waste products of metabolism and plasma water) from the dialyser.
The dialysis liquid is prepared by a metered mixing of water and two concentrated solutions containing the principal electrolytes of blood. The mixture is maintained at a substantially constant temperature by heating the water, and, in some machines, it is filtered in such a way that the liquid circulating in the dialyser is free from microorganisms and pyrogenic elements. The fresh filtered dialysis liquid can be filtered a second time to serve as perfusion liquid.
A dialysis machine comprises a hydraulic circuit consisting of an assembly of lines, pumps, valves, filters, etc., which are susceptible to clogging, which is likely to favour the development of undesirable bacterial flora. It is expedient to filter the dialysis liquid, because even if the blood in a dialyser is isolated from the dialysis liquid by a semipermeable membrane which in principle does not allow the bacteria to pass through, contamination of the blood is still possible in the event of microscopic leakages in the membrane. In addition, the bacterial derivatives of low molecular weight can pass through the membranes of the dialysers.
The zones of the machine which are the most prone to clogging are the filters which are used to filter the dialysis liquid, and in the first chamber of which all the materials stopped by the membrane of these filters are concentrated, as well as the whole circuit for removal of the used liquid which is in contact with organic substances (waste products of metabolism, plasma water).
The present-day dialysis machines are therefore equipped with a disinfection system which makes it possible to fill the hydraulic circuit with a disinfection liquid, then to purge it of this liquid, after the disinfectant has stagnated therein for a defined period of time. The hydraulic circuit is then flushed with water and remains filled with water until the machine is next used. In general, the machines are disinfected between two dialysis sessions. After the final dialysis session of the day, depending on the type of disinfectant used, the machines either remain filled with disinfection liquid for the night, or they are flushed with water after disinfection and remain filled with water for the night. The difference in treatment stems from the fact that some disinfectants (for example chlorine-based disinfectants) are corrosive and their prolonged stagnation in the machine would damage its hydraulic circuit.
There is a drawback to leaving the machines filled with water for several hours: if the disinfection has not eliminated all the microorganisms present in the hydraulic circuit, the surviving microorganisms will be able to multiply and colonize some zones of the circuit where the disinfection action is less effective.
On the other hand, the chlorine-based disinfectants, such as Javelle water, are reputed to be the most effective, and they have an additional effect of cleaning the circuit (organic deposits), an effect not possessed by the other disinfectants currently used (aldehyde-based disinfectants, and disinfectants based on peracetic acid).